..and pixel art in general, that really grabs you? Is it that crisp look that you can't get with a shrunken-down, million-color image? Maybe it's the fun of imitating a game you like, pretending your character is part of it (especially you Mugen players). Is it the nostalgia factor, like how the good old games of the 80s and 90s were done in pixels? Perhaps you just like it as an overall style.
Maybe you like building it as much as you like looking at it - do you enjoy how editable and easily changeable a sprite is, even when it seems like it's finished? Are you fascinated by how you can do so much with so little (the Lego effect) - and how certain techniques like antialiasing and selective dithering can make something so simple look so professional? Do you like pretending to be confined to classic 16-bit specs (or 8bit, etc), like using only a 15-color palette with 1 background color? Maybe it's how the small size forces you to be simple and use only the most basic elements to communicate (sometimes big anime eyes, simple hair rendering, simple cloth folds, etc). Or maybe it's how easy it is to animate for the web.
It just goes on and on, and doubtless every pixel fan has some unique reason that they like it. There's this 'collectibility' aspect to it all - like little digital baseball cards - that seems to get people addicted. Then people find out they can do it themselves. Then they get good at it and they're caught forever. What's your story?